1. Field of the Invention
This invention relates to a locking mechanism for fixing an outer part on an inner part, especially the coupling sleeve of a driveshaft of an agricultural implement to the power take-off shaft of a tractor, the locking mechanism comprising locking members which are guided in apertures in the outer part so as to be movable in a radially limited way and which, in the locked position, are supported in a radially outwardly direction on an inner bore face of a movable locking ring of the locking mechanism, which locking ring is loaded by the force of a spring of the locking mechanism into the locking position, the spring acting on the one hand on the outer part and on the other hand on the locking ring, the locking members extending radially inwardly from the apertures into a receiving bore of the outer part and projecting, for fixing purposes, into a recess in the inner part, and the locking mechanism also comprising means for retaining the locking ring in an open position clear of the apertures for the locking members and for automatically cancelling the retention when the inner part is introduced into the receiving bore of the outer part.
2. Description of Prior Art
For example, from the German Patent Specification No. 34 08 852 a locking mechanism retainable in the open position is known in which the receiving bore of a coupling sleeve accommodates a supporting ring which is loaded by the force of a spring in the direction of the apertures. When a power take-off shaft is disconnected from the coupling sleeve, this supporting ring is positioned in the region of the apertures and prevents the locking members (designed as balls) from moving radially inwardly. It holds, therefore, locking members in the radially outward position, wherein the locking members, as a kind of stop, prevent the locking ring from being moved under the spring force into the region of the apertures. When inserting the power take-off shaft into the receiving bore of the coupling sleeve, the power take-off shaft causes the supporting ring to be moved further into the bore of the coupling sleeve, as a result of which the supporting ring releases the locking members enabling them to fall radially inwardly into the locking recess provided in the power take-off shaft and subsequently permitting a displacement of the locking ring by means of the locking members. The disadvantage of this design is that the receiving bore of the supporting sleeve additionally has to be provided with a supporting ring which takes on a locking function in the open position. This results in a complicated design and, in addition, the force of the spring holding the supporting ring in the locking position has to be overcome during the process of insertion.
It is therefore the object of the present invention to propose a simple locking mechanism in the case of which the interior of the receiving bore for the inner part or power take-off shaft to be received is completely free from any locking components.